In recent years, sound collecting devices using a plurality of microphones have been used in vehicles such as robots and automobiles. By using a sound collecting device in a vehicle, a user can provide instructions to the vehicle in a hands-free fashion.
In such a state, the sound collecting device acquires a target sound by performing signal processing (array process) on observation signals obtained by a plurality of microphones. As the signal processing, for example, a sound source separation process using an independent component analysis, a principal component analysis or the like, or a static or dynamic beam-forming is used.
However, vibrations caused by the motor, the engine, and/or the like of the vehicle as well as vibrations caused by interference with the external environment (such as road surfaces and obstacles) reach the microphones. As a result, vibration sounds are mixed as a noise into the observation signals obtained by the microphones, thus making it difficult to acquire the target sound at a satisfactory level.
Therefore, Patent literatures 1 to 3 disclose techniques to suppress vibration sounds by observing vibrations by using a vibration observation device, generating a vibration signal by carrying out signal processing using the observation result, and subtracting the vibration signal from the observation signal obtained by the microphone for a target sound.
Incidentally, Patent literature 4 discloses a technique in which a plurality of microphones are arranged in a regular triangle configuration.